Process for the production of a coated product, thin-walled coated cylinder obtained by using said process, and an ink transfer roller comprising such a cylinder

ABSTRACT

Process for the production--using plasma spraying--of a coated product in which the coating consists of a ceramic fluorocarbon polymer-comprising coating, while between the surface of the product and the ceramic fluorocarbon polymer-comprising coating an adhesion layer completely of metal is applied. The adhesion layer consists in particular of at least two metals reacting exothermally with each other under plasma spraying conditions. In particular, the product to be coated is a thin-welled nickel, seamless cylinder with a wall thickness of 50-220 μm. The invention also relates to an ink transfer roller in which a thin-walled seamless cylinder obtained by the process according to the invention is used.

The invention relates to a process for the production of a coatedproduct, in which a metal-comprising adhesion layer and aceramic-fluorocarbon polymer-comprising coating are applied to saidproduct by means of plasma spraying.

Such a process is known from U.S. Pat. No. 4,566,938.

The above-mentioned patent describes the application to a roller of anadhesion layer in the form of a mixture of a metal and a fluorocarbonpolymer, followed by the application of a ceramic-fluorocarbonpolymer-comprising coating. Such a known process has the disadvantagethat it can be used only for the coating of rigid products which are notmechanically deformable in normal circumstances. If such a process isused for the coating of a flexible product, adhesion problems betweenthe coating system and the substrate occur during use, which can lead tocracking of the coating layers and even to partial peeling thereof.

The object of the present invention is to produce a solution to theabove problem, so that the process can be used for coating flexibleproducts without the coatings applied cracking or peeling during normaluse of the coated flexible product.

The process is to that end according to the invention characterized inthat an adhesion layer consisting entirely of metal is applied betweenthe surface of the product to be coated and the ceramic-fluorocarbonpolymer-comprising coating.

It was surprisingly found that the deformation stability of theceramic-fluorocarbon polymer-comprising coating increases veryconsiderably if an adhesion layer made entirely of metal is used, unlikethe use of an adhesion layer consisting of a mixture of fluorocarbonpolymer and metal specified in the above-mentioned U.S. Pat. No.4,566,938. This greatly improved stability is particularly evident ondeformation of the substrate to which the adhesion layer and theceramic-fluorocarbon polymer-comprising coating have been applied. Withnormal elastic deformation of the substrate, cracking and possiblypeeling no longer occur.

In particular, the process according to the present invention ischaracterized in that the metal adhesion layer is formed using at leasttwo metals reacting with each other exothermally under plasma sprayingconditions.

In that case the adhesion layer expediently consists of anickel-titanium alloy.

Another very useful adhesion layer is formed by a nickel-aluminiumalloy.

In such a nickel-titanium and nickel aluminium adhesion layer themolecular ratio nickel:titatiun or nickel:aluminium is advantageouslybetween 30:70 and 70:30 respectively.

The ceramic constituent of the ceramic-fluorocarbon polymer-comprisingcoating in the process according to the invention is very advantageouslyselected from amorphous metal oxides, metal carbides, metal nitrides andmetal silicides or mixtures of such substances.

On account of the mechanical properties of the ceramic-fluorocarbonpolymer-comprising coating, it has been found advantageous to useamorphous starting materials for the ceramic constituent. It was foundthat the elasticity of the coating increased particularly if, instead ofa crystalline ceramic material, an amorphous ceramic material was used.It was also found that the amorphous nature of the starting materialswas retained during the plasma spraying treatment and any furthertreatments.

In a particular embodiment of the process according to the invention theproduct to be coated is made of metal between 10 and 1000 μm thick, onwhich first by plasma spraying a Ni/Ti adhesion layer is formed with 50mol.-% Ni and 50 mol.-% Ti and between 25 and 500 μm thick, followed bya coating consisting of a thorough mixture of metal, ceramic andfluorocarbon polymer between 75 and 800 μm thick, in which the metalconsists of a Ni/Ti alloy with 50 mol.-% Ni and 50 mol.-% Ti, theceramic part consists of 1-80 wt.-% amorphous titanium dioxide and 99-20wt.-% amorphous aluminium oxide, and the composition over the thicknessof the coating starting from the adhesion coating or first coatingvaries from 85-0% metal and 10-95% ceramic, while at least 5 wt.-%polytetrafluoroethylene is always present.

The metal of the substrate can, for example, be steel, copper, nickel,aluminium and other commonly used metals and metal alloys.

There are multiple uses for such flexible metal products provided with aceramic-fluorocarbon polymer-comprising coating. The process describedabove can be used in all cases where a thin flexible metal object mustbe provided with a very strongly adhering, noncracking, electricallyinsulating, wear-resistant coating layer with low coefficient offriction. One example is the coating of mechanically loaded surfaces inequipment of many kinds; in particular in the full or partial coating ofsurfaces of rollers the products obtained by means of theabove-described process will be of great use.

In another special embodiment to the process of the invention, theproduct to be coated is a thin-walled nickel seamless cylinder with awall thickness between 50 and 250 μm.

Such a thin-walled nickel seamless cylinder obtained can be applied,with suitable means known in the art, as a lining on, for example, aroller. Such a roller is provided with a number of gas outflow openingsat least at one of the ends of the roller. These gas outflow openingsare connected via the inside of the roller to a supply of gas underincreased pressure. If the thin-walled cylinder is now slid over a shortdistance onto the roller, thereby covering the gas outflow openings, andthe gas supply to these openings is then opened, the thin-walled nickelcylinder is slightly elastically stretched, so that with simple meansthe thin-walled cylinder can be slid over the entire length of thesupporting roller.

A slightly conical-shaped thin-walled cylinder which can be slid onto anopposite slightly conical-shaped supporting roller can also be selected.

In connection with the above, it is also pointed out that theapplication of an adhering ceramic-fluorocarbon polymer-comprisingcoating to a metal product offers very good posibilities for manyapplications; the use of the process according to the invention is not,however, limited to the application of said coating to a metal product.The process for the application of a very strongly adheringceramic-fluorocarbon polymer-comprising coating using an adhesion layerconsisting entirely of metal can be carried out just as successfully forthe coating of a plastic-based material. In the latter case it could,for example, be a glassfibre-reinforced polyester material, in which theglassfibre content is made as high as possible, on account of the plasmaspraying conditions.

The invention also relates to a thin-walled cylinder obtained using theprocess described above, which is characterized in that, afterapplication, the ceramic-fluorocarbon polymer-comprising coating bymeans of beam treatment is provided with a surface pattern of cavitiesof the desired shape.

Such a thin-walled coated cylinder is used, inter alia, in ink transferrollers such as those described below. The form and application ofinking rollers is known per se from the earlier-mentioned U.S. Pat. No.4,566,938. For use in an inking roller such a thin-walled cylinderproduced by the process according to the invention can be applied to asubstrate in the form of a roller, in the same way as described abovefor a thin-walled cylinder not provided with a surface pattern ofcavities. With the use of such a thin-walled coated cylinder in an inktransfer roller there could also be other fastening means to give thethin-walled cylinder the necessary rigidity. Instead of fastening meansin the form of a support, tensioning means fixed in the ends of thecylinder can be selected so that the cylinder can be tensioned in such away that the surface has sufficient rigidity to permit its use as aninking roller. In order to obtain the necessary rigidity, one can alsoopt for the use of fastening means for the cylinder which make itpossible to place the inside of the cylinder under liquid or gaspressure. In the case of gas pressure the relevant safety regulationswill, of course, have to be observed.

In connection with the above-described use of a thin-walled coatedcylinder provided with a surface pattern of cavities, also is referredto Dutch Patent Application No. 8,401,401 of Applicants, which describesa process for the production of a screen roller. The said applicationdescribes a thin-walled cylindrical sieve which is fitted in clampingfashion to a bearing cylinder by first sealing the perforations of thesieve, then fitting the sieve by means of the earlier-described airslide-on method around a roller provided with openings, and subsequentlyremoving the filling from the perforations of the sieve. The inkingroller obtained in that way therefore uses a fully perforated cylinderas the thin-walled seamless cylinder, so that the cavities pattern inthe cylinder is determined by the properties of the thin-walled cylinderitself. However, in the process according to the present invention isstarted from a completely closed thin-walled cylinder, around which avery strongly adhering, mechanically durable ceramic-fluorocarbonpolymer-comprising coating is applied, whereby after application of theceramic coating the form and fineness of the surface pattern of cavitiescan be freely accepted.

The invention also relates to an inking roller, comprising a substratehaving applied thereto a metal-containing adhesion layer and a ceramicfluorocarbon polymer-comprising coating, the latter being provided,after application, with a surface pattern of cavities by means of beamtreatment, characterized in that it is formed from a thin-walled coatedcylinder which is provided with a surface pattern of hollows of thedesired shape and has fastening means for the said cylinder and sealingmeans, permitting its use as an ink transfer roller as described above.

The above-described inking roller expediently has sealing means, atleast having a sealing element to prevent penetration of ink between thefastening means and the cylinder, and a pressure member for such anelement. An example of a sealing device such as that referred to aboveis a plate which is fixed on the shaft of the inking roller, by means ofwhich a sealing ring is pressed against the dividing seam between thethin-walled cylinder and its support.

In particular, the ink transfer roller has sealing means in the form ofa sealing cuff, formed by a disc which can be fixed on the shaft of thesupporting roller and a flange which is fitted perpendicular to the discand can connect to the outer surface of the sleeve in the form of aseamless cylinder fixed on the supporting roller, while at least oneannular sealing element between cylinder surface and inside of theflange ensures sealing.

In such a cuff the sealing ring is advantageously made ofpolytetrafluoroethylene, at least on its surface. Use ofpolytetrafluoroethylene is very advantageous on account of the use ofthe inking roller in combination with inks which may contain aggressivecompounds such as solvents.

With the use of the ink transfer roller according to the inventionwhich, as indicated, may consist of a thin-walled cylinder applied to asolid supporting roller, the problem can arise that ink applied with theroller creeps through capillary action between the cylinder and thesupporting roller. This ink can dry there and, if the quantity thereofis sufficiently great, can give rise to irregularities in the surface ofthe thin-walled sleeve. During use of such an inking roller, itgenerally turns in a tank containing ink or dye, so that dye is taken upwhile the excess is scraped off, for example with the aid of a steelsquegee. Unevennesses in the surface of the thin-walled sleeve due toink penetration can lead to excessive wear of squeegee and/or sleeve,and in serious cases can lead to tearing away of the thin-walled sleevefrom the surface of the bearing roller. In any case the penetration ofink between thin-walled sleeve and bearing roller must therefore beavoided. Through the use of the above-mentioned sealing means such inkpenetration is effectively prevented.

It is pointed out that the above-described sealing means can be veryadvantageously used in combination with an ink transfer roller formedaccording to the invention; the use is not, however, restricted to that.Use can also be made of the cuff for other rollers which are providedwith a detachable inking surface.

The invention will be explained in greater detail below with referenceto the drawing, in which:

BRIEF DESCRIPTION OF THE DRAWING:

FIG. 1 shows a cross section through an inking roller according to theinvention with a sealing cuff provided thereon;

FIG. 2 shows a cross section on an enlarged scale through the wall of athin-walled cylinder used according to the invention.

In FIG. 1 the inking roller is indicated by reference number 1, while 2,3 and 4 indicate the roller element, the shaft journal and the shaft.Disposed on the roller element is a thin-walled cylinder 5 provided witha cavity pattern. Reference numbers 6 and 7 indicate the disc and theflange connecting to the outer surface, with the sealing ring 8 takingcare of the sealing which prevents ink from penetrating between thethin-walled cylinder clamped on the supporting roller and the supportingroller.

FIG. 2 again indicates by 5 the wall of the thin-walled cylinder shownin FIG. 1, 11 indicates the earlier-discussed adhesion layer of metal,and 12 is the ceramic-fluorocarbon polymer-comprising coating applied tothe adhesion layer.

I claim:
 1. An ink transfer roller comprising a thin-walled coatedcylinder obtained by a process in which an adhesion layer consisting ofmetal and a coating comprising a mixture of a ceramic and fluorocarbonpolymer are each applied by means of plasma spraying to a cylinder to becoated, said adhesion layer being between the surface of said cylinderto be coated and said coating, said adhesion layer being formed byplasma spraying using at least two metals reacting with each otherexothermally under plasma spraying conditions, said coating beingprovided with a surface pattern of cavities by means of beam treatment,said roller also comprising fastening means for said cylinder enablingsaid cylinder to be used as an ink transfer roller, said ink transferroller further having sealing means to prevent deposition of ink betweensaid cylinder and said fastening means.
 2. The ink transfer roller ofclaim 1, in which the sealing means comprises a sealing element and apressure member for said sealing element.
 3. The ink transfer roller ofclaim 1, wherein:the cylinder to be coated is a metal cylinder with awall thickness between 10 and 1000 μm; said adhesion layer is between 25and 500 μm thick, and consists of a nickel/titanium alloy in a 50:50molar ratio; said coating consists of a mixture of metal, ceramic, andfluorocarbon polymer and has a total thickness between 75 and 800 μm,the metal being a nickel/alumimum alloy in a 50:50 molar ratio, theceramic being between 1 and 80% by weight of the total ceramic contentamorphous titanium oxide and between 99 and 20% by weight of the totalceramic content amorphous aluminum oxide, the fluorocarbon polymer beingpolytetrafluoroethylene; and the composition over the total thickness ofthe metal/ceramic/fluorocarbon coating varies from 85-0% metal and10-95% ceramic, with at least 5% by weight polytetrafluoroethylenealways being present.
 4. An ink transfer roller comprising:a thin-walledcoated cylinder obtained by a process in which an adhesion layerconsisting of metal and a coating comprising a mixture of a ceramic andfluorocarbon polymer are each applied by means of plasma spraying to acylinder to be coated, wherein said adhesion layer is between thesurface of the cylinder to be coated and said coating, said adhesionlayer being formed by plasma spraying using at least two metals reactingwith each other exothermally under plasma spraying conditions, and saidcoating being provided with with a surface pattern of cavities by meansof beam treatment; fastening means for said cylinder enabling saidcylinder to be used as an ink transfer roller, said fastening meansconsisting of a roller which supports said cylinder, said roller havinga shaft; sealing means to prevent deposition of ink between saidcylinder and said fastening means, said sealing means comprising asealing element and a pressure member for said sealing element; saidpressure element being a cuff formed by a disc which can be fixed onsaid shaft of said supporting roller and a flange which is fittedperpendicular to said disc, said flange being abble to be connected tothe outer surface of said cylinder fixed on the supporting roller; andsaid sealing element being at least one annular element between thesurface of said cylinder and the inside of said flange, at least thesurface of said sealing element being of polytetrafluoroethylene.
 5. Theink transfer roller of claim 4 wherein at least the surface of saidsealing element is of polytetrafluoroethylene.